IPT systems are well known. The operation of such systems in described, for example, in U.S. Pat. No. 5,293,308, the disclosure of which is incorporated herein by reference. IPT systems typically have a primary conductor (often in the form of a pathway or track) which is energised with an alternating current so that a time-varying magnetic field is produced. One or more pick-up circuits are provided which receive power inductively from the primary conductor. Each pick-up includes a pick-up coil in which a voltage is induced from the primary conductor. The pick-up coil is tuned with a tuning capacitance to be resonant at the frequency of the current in the primary conductor. An output of the pick-up supplies a load.
In some applications it is desirable to have a significant power supply of both alternating current (AC) and direct current (DC) as independently controllable outputs of a single pick-up device. One example is that of powering a class of luminaries commonly called “Intelligent Lights”, for which both DC and AC power are required. In contrast to conventional lights, Intelligent Lights have motors and control circuitry which require a DC source in addition to the AC power driving the lamp itself. Various lamps are commonly used for such purpose that can include 1.2 kW AC supply for driving the lamp, a 24V, 200 W DC supply is required to run the control circuits.
U.S. Pat. No. 7,781,916 discloses an IPT system pick-up which provides two independently controllable outputs. As stated in that publication, the intention is to provide two DC outputs, one being a high voltage DC output for supplying a primary load, and the second output being a low voltage DC output which is only required for low power purposes such as supplying control circuitry. The problems exists that the circuit disclosed in U.S. Pat. No. 7,718,916 is unsuitable for providing two or more significant power supplies, and is not satisfactory for providing an efficient high power AC power supply as well as an DC supply.
Object
It is an object of the present invention to provide an IPT pick-up, or an IPT system including a pick-up, which overcomes or ameliorates one or more the disadvantages of existing constructions. Alternatively, it is an object of the present invention to at least provide a useful alternative to existing constructions.